The OEM exhaust specs out like this:
moving vehicle = apr. 75 db
stationary vehicle = 92 db at 6.225 1/min
value of backpressure = 0,47 bar at 2. gear and 0,51 bar at 3. gear
weight of the muffler = apr. 21 kg
The Sport system is not numerically louder, just much deeper and better sounding than the OEM system. It's perfect for those who want a better sound, without extra sound volume.
Obviously, it's not common for manufacturers to take the time to measure decibel and backpressure values, but this should give you some perspective with Eisenmann systems VS stock.